Electric switch



Dq-sc 11, 1956 F. BAUER ELECTRIC SWITCH Filed July 20, 1954 Y MPM T M mwmm m Z n&4 m. FQ V. B

United States Patent 1 2,773,950 ELECTRIC SWITCH Franz Bauer, Vienna, Austria Application July 20, 1954, Serial No. 444,613 Claims priority, application Austria August 5, 1953 4- Claims. (Cl. 20021) U. S. Patent No. 2,684,412, describes an electric switch with a cam-actuated switch bridge, the distance of which from the switch spindle is altered when the switching movement is eflected, there being provided between the control cam and the switch bridge a roller which moves the control cam and which has a spindle of smaller diameter than the roller and which is guided in parallel projections on the switch casing so that it is prevented from moving transverse to the switching direction. According to that specification, the roller spindle is operatively connected to the switch bridge more or less only in the switching direction, that is to say in such manner that practically only that component is transmitted, of the roller-actuating force, which is effective in the switching direction. This arrangement results in the switch bridge not being subjected to lateral forces, provided that those small frictional forces which are due to the rotation of the roller spindle in the movable bridge part, are taken up by a guide member connected to the switch bridge and known as the thrust rod. In contrast with hitherto known constructions, however, the said friction forces are very small, this point being of considerable importance as bearing upon the operational life of the switch.

As the construction described in the aforementioned specification has very considerably reduced lateral stressing of the impulsing rod, the need has been seen of omitting the said thrust rod altogether and to mount the roller directly in an extension of the switch bridge. This step provides a switch wherein the frictional forces due to the rotation of the roller are no longer taken up in their entirety, being transmitted to the switch bridge and imparting thereto at the beginning of the lifting movement 1 thereof a tilting moment which, however slight, is sufficient to disturb the simultaneous opening of the two contact points formed by the switch bridge. The first contact to open therefore has to be big enough to deal with the total rupturing capacity, with the result that, despite the short duration of this occurrence, switches of this type can only be used for relatively low currents.

According to the invention, the switch bridge can be completely relieved of lateral stresses, even when no laterally guided impulsing rod is present, of the roller spindle guided in parallel slots in the switch body and the bridge, likewise guided in parallel slots in the switch casing, are in articulated connection through the agency of an intermediate member.

A constructional example of the invention is illustrated in the accompanying diagrammatic drawings, Fig. 1 being an end elevation and Fig. 2 a corresponding side view. In the drawings (Fig. 2), 1 designates the switching body (omitted from Fig. 1) which may have, for example, the form described in detail in patent specification of U. S. Patent No. 2,684,412. The switch spindle 3 carries a switching cam 4 co-operating with one or more pressure rollers 5. The roller 5 is carried on a shaft 9 and may be formed in one piece therewith. The roller shaft 9 projects laterally beyond the arms of the fork 8, the said arms resting upon the roller spindle 9, and is guided in slots fashioned in any suitable manner in the switch casing. As opposed to the construction described in the aforementioned specification wherein the thrust rod upon the roller shaft must have greater lateral play than has the roller shaft in the guided slots in order to obviate, upon rotation of the cam, the efiect upon the lateral guide surfaces of the component of force transverse to the switching direction, the inevitably present bearing clearance of the shaft 9 in the fork arms 8 is of itself sutficient in the construction according to the present invention, since the connecting member 8 does not have any lateral guide surfaces.

The forked part 8 has an extension 40 which may also be forked and in which a pivot pin 41 is mounted. The latter extends through forked extensions 42 of the switch bridge 15 (which co-operates with the contacts 25) and projects on both sides into the guide slots 20 in the casing 1.

While the roller spindle 9 rolls along the wall slots 20 to absorb the lateral cam induced forces when switching is effected, the bridge 15 is free of lateral forces and substantially devoid of any turning moment, being guided by the pin 41 rubbing in the slots 20. Thus, if the two contact pressure springs 18 are of equal strength, the construction according to the invention must cause the two rupturing points 18 and 25 to open uniformly and simultaneously. The kinematic processes may be explained as follows. The roller 5 rotated by the cam 4 also tries to rotate the part 8, but the part '8 cannot be rotated because the rotation thereof is opposed by the pivot pin 41 which is guided in the switch casing.

In Figure 1, the connecting member 8 is guided upon the roller shaft 9 and upon the pivot pin 41 by means of forked slots. Instead of using the guiding slots, it is possible for the intermediate member to surround the roller shaft 9 and (or) the pivot pin 41 in the manner of a lug and to be mounted thereon. The bearing bridge can be fitted in forked fashion to the pivot pin 41 instead of being secured thereto by means of bearing lugs.

What I claim is:

1. In an electric switch comprising a casing, 21 rotatable switching control cam mounted therein, at least one contact bridge movably mounted in the casing in spaced relation to the control cam, movement of each bridge under the control of the cam causing a switching operation: a positive mechanical means operatively interconnecting the control cam and each contact bridge, said means including a roller in contact with the cam; a transverse shaft for mounting the roller, the shaft being guided in parallel guide means in the casing, the guide means being arranged to guide the shaft and roller in a straight path between the cam and the contact bridge and preventing any transverse movement thereof; a link having one end pivotally mounted on the shaft; and a transverse pin arranged to control the movement of the bridge, the other end of said link being pivotally mounted on the pin and the pin being guided in parallel guide means in the casing, the latter guide means being arranged to guide the pin in a straight path between the cam and the contact bridge, and lateral actuating forces exerted upon the interconnecting means being absorbed by the guide means in the casing.

2. The electric switch of claim 1, wherein the one link end is a fork-like portion surrounding the roller shaft and the other link end is a fork-like portion surrounding the pin.

3. The electric switch of claim 1, wherein the contact bridge has a lug-like extension in connection with the pin.

4. The electric switch of claim 1, wherein said guide means for the roller shaft and the pin is formed by a common guide groove in the casing.

Hartmann Aug. 10, 1915 Farmer June 16, 1942 

